1. Postdoctoral Fellow, Civil and Environmental Engineering Dept., Univ. of California Los Angeles, Los Angeles, CA 90095.
2. Civil Engineer, City of Los Angeles, Los Angeles World Airports, Los Angeles, CA 90045.
3. Professor, Civil and Environmental Engineering Dept., Univ. of California Los Angeles, 5714 Boelter Hall, Los Angeles, CA 90095-1598 (corresponding author). E-mail: stenstro@seas.ucla.edu